My 2005 used to do this alot , when in 5 th gear at 3,000 rpm if you puch it sometimes i would get a very violent buck. After i had my ECU flashed the problem never came back so i would agree with Warrtalon and say its fuel cut . But your dynoflashed , maybe its your tune , did it buck before the tune ?

 

check the boost level. it's been a lot colder out here, and your boost may have creeped up if you're using a MBC.

 

That is exactly what it is. I just took a drive to diagnose it, and it will show about 23psi in the upper gears, but bucks when it hits about 29psi in the lower gears.

My Forge MBC is turned all the way down. =( I guess this is the reason as to why I have always had electronic controllers up until now. Any solutions for my MBC other than buying an electronic one?

 

First check to make sure that the hoses for the MBC haven't blown off. It's odd that despite being turned all the way down, your boost still hasn't come down. If the hoses are OK, switch out the spring in the MBC.

 

I checked the hoses and they are fine. The boost controller was turned down all of the way already, so there is nothing else I can do to adjust it. I think I will just pick up an electronic controller....I don't want to deal with that thing being all over the place like this.

 

Oh, if you are spiking to huge boost like that, then the MBC needs to be cleaned. It has nothing to do with having an MBC instead of EBC.

Take the UNOS apart, ensure the spring is seated on the nipple, clean out the bleed hole (ensure no debris left over from manufacturing), and grease the ball some before putting it back together. There is NO good reason for you seeing 29psi (holy cow) in lower gears but only 23 psi in higher gears. It should be the opposite, but since it's not, then you have a definite mechanical problem.

Earlier, you said you have been scouring for boost leaks. Does that mean you create a boost leak tester and performed a boost leak test up to 25psi with no hint of leaks, or were you saying you just "looked" for leaks and couldn't find them. There is only one way to look for boost leaks...